High temperature bis(epoxyalkyl)carborane adhesives

ABSTRACT

THE PROCESS OF PROVIDING AN ADHESIVE JUNCTION BETWEEN TWO WORKPIECES HAVING OPPOSING SMOOTH SURFACES COMPRISING THE STEPS OF MIXING MATERIAL SELECTED FROM THE GROUP CONSISTING OF BIS(EPOXYBUTYL)CARBORANE, BIS(EPOXYPENTLY)CARBONANE, AND BIS(EPOXYHEXYL)CARBORANE, WITH A CURING AGENT SELECTED FROM THE GROUP CONSISTING OF BORON TRIFLUORIDE ETHYLAMINE AND 4,4&#39;&#39;-DIAMINODIPHENYLSULFONE, APPLYING SAID MIXTUE TO THE OPPOSING SURFACES, JOINING THE SURFACES AND ALLOWING THE WORKPIECES WITH THE MIXTURE THEREBETWEEN TO HARDEN UNDER HEAT AND PRESSURE.

United States Patent Olfice 3,823,095 Patented July 9, 1974 US. Cl. 260-2 N 2 Claims ABSTRACT OF THE DISCLOSURE The process of providing an adhesive junction between two workpieces having opposing smooth surfaces comprising the steps of mixing material selected from the group consisting of bis(epoxybutyl)carborane, bis(epoxypentyl)carborane, and bis(epoxyhexyl)carborane, wlth a curing agent selected from the group consisting of boron trifluoride ethylamine and 4,4'-diaminodiphenylsulfone, applying said mixture to the opposing surfaces, joining the surfaces and allowing the workpieces with the mixture therebetween to harden under heat and pressure.

The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; 42 U.S.C. 2457).

This is a division of application Ser. No. 112,821, filed Feb. 2, 1971, which is a division of Ser. No. 762,614, filed Sept. 25, 1968, now US. Pat. No. 3,669,993.

The present invention relates to the preparation of bis (epoxyalkyl)carborane monomers, alkenyl intermediates leading to these monomers, and formulations based on these monomers which are useful for room temperature and high-temperature adhesive applications.

Generally speaking, bisalkylcarborane intermediates which are the subject of the present invention have the following structure These are:

(a) x=1; 1,2-Bis(2-propenyl)carborane (b) x=2; l,2-Bis(3-butenyl)carborane (c) x=3; 1,2-Bis(4-pentenyl)carborane (d) x=4; 1,2-Bis(5-hexenyl)carborane (e) the isomeric compound 1,7-bis(3 butyenD-neo-carborane.

These compounds can be converted to the corresponding terminal epoxy derivatives having the following structure oHP-cmcmpo momma-cm O lOHlO The following compounds are also characterized herein.

These epoxies can be cured to hard solids by catalysts and/or reactive hardeners to form a polymer having the following repeating unit in its general structure.

L31 ioHio CH2 HO- It is also to be observed that polymers from monoepoxyalkylcarboranes have been investigated and displayed no adhesive properties. These monoepoxyalkylcarboranes have the following repeating structural formula.

CHa0HO- The synthesis of carborane C B H which is the has material for the present invention has been described in a series of articles appearing in the 1963 December issue of Inorganic Chemistry.

Carborane can be converted to a series of bis(alkenyl) carboranes using a dilithium derivative in accordance with the following reactions:

O B io m 1810 10 Bisalkenylcarboranes where x=1, 2, 3, and 4 were prepared in this way. In addition, the bisbutenyl-derivative (x=2) of meta(neo)carborane was also prepared. The following illustrative examples are given with regard to the preparation of these compounds.

EXAMPLE 1 1,2-Bis (3-butenyl) carborane: x= 2 A slight excess of 1.6M butyllithium solution in hexane '(135 ml. or 0.216 moles of BuLi) was transferred to a dropping funnel in a nitrogen-filled glove bag. The solution was added over a 15-minute period, with stirring, to 11.5 g. (0.0800 moles) of carborane dissolved in ml. of anhydrous ethyl ether contained in a round bottom reaction flask. During addition, a nitrogen flow was maintained over the system, and the flask was cooled with an ice-water bath. After addition was complete, the suspension of heavy white solid was stirred at room temperature for one hour. The suspension was allowed to settle, and the bulk of the supernatant liquid was removed with a syringe. About 75 ml. of anhydrous ethyl ether was added to the system with stirring to wash the solid. The bulk of the solution was removed, and the procedure was repeated. About ml. of anhydrous ethyl ether was added, and the mixture was heated to reflux. A weighed quantity of 4-bromo-1-butene (27.0 g.--0.200 moles) was added to the system over a 10-minute period. After a two-hour reflux period, the reaction mixture was poured into 200 ml. of water and thoroughly mixed. The ether layer was separated and dried with magnesium sulphate. The crude product, obtained from the removal of the ether solvent on a rotary evaporator, was fractionally distilled under vacuum (0.1 mm.) andthe fraction which evolved at a head temperature of 150-170 C. was collected and crystallized. The colorless solid (14.3 g. representing a 76 percent conversion of carborane to desired product) had a m.p. range of 70-72 C. Gas chromatographic and infrared analyses indicated that the sample was 98 percent pure and an elemental analysis was in excellent agreement with the expected values.

Calcd. for B C H B, 42.8; C, 47.7; H, 9.5. Found:

B, 42.4; C, 48.2; H, 9.5.

EXAMPLE 2 1,2-Bis (4-pentenyl carborane: x: 3

The procedure described above for the preparation of bis(butenyl)carborane was followed using the following amounts of reagents.

125 ml. butyllithium solution (0.200 moles of BuLi) 11.5 g. carborane (0.0800 moles) 27.0 g. S-bromo-l-pentene (0.180 moles) The crude product was distilled under vacuum (0.1 mm.) and the fraction which evolved at a head temperature of 150 C. was collected as a colorless liquid (18 g. representing a conversion of 72 percent carborane to desired product). Gas chromatographic and infrared analyses indicated that the product was 93 percent pure.

EXAMPLE 3 1,2-Bis(5-hexenyl)carborane: x=4

The procedure described above for the preparation of bis(butenyl)carborane was followed using the following amounts of reagents.

150 ml. butyllithium solution (0.240 moles of BuLi) 14.4 g. carborane (0.100 moles) 32 g. 6-bromo-l-hexene (0.20 moles) The crude product was distilled under vacuum (0.1 mm.) and the fraction which evolved at a head temperature of 180 C. was collected (26.8 g. of colorless liquid representing a conversion of 87 percent carborane to desired product). Gas chromatographic and infrared analyses indicated that the product was 96 percent pure.

EXAMPLE 4 1,2-Bis(2-propenyl carborane: x: 1

The procedure described above for the preparation of bis(butenyl)carborane was followed except that a longer reflux time (24 hours) was employed. The following amounts of reagents were used.

150 ml. butyllithium solution (0.240 moles BuLi) 14.4 g. carborane (0.100 moles) 29 g. allylbromide (0.24 moles) The crude product was distilled under vacuum (0.1 mm.) and the product which evolved at a head temperature of 150 C. was collected (40 g. of a colorless liquid representing a conversion of 18 percent carborane to desiredproduct). Gas chromatographic and infrared analyses indicated that the sample was 93 percent pure.

5.8 g. carborane (0.040 moles) 10.8 g. 4-bromo-1-butene (0.795 moles) The crude product was distilled under vacuum (0.1 mm.) and the fraction which evolved at a head temperature of 150 C. was collected (6.2 g. of a colorless liquid representing 60 percent conversion of carborane to desired product). Gas chromatographic and infrared analyses indicated that the product was 93 percent pure.

Bis(alkenyl)carboranes could be converted to the corresponding terminal bis(epoxyalkyl)carborane monomers by treatment with trifluoroperacetic acid under carefully controlled buffer conditions in the following manner O B ioHio Bis(epoxyalkyl)carboranes where x=1, 2, 3, and 4 were prepared in this way. In addition, the bis(epoxybutyl) derivative (x=2) of meta (neo) carborane was prepared. This is the first reported preparation of these compounds.

EXAMPLE 6 1,2-Bis (epoxybutyl carborane: x=2

Trifiuoroperacetic acid was prepared in the following manner. Sixty ml. of methylene chloride was added to 4.4 ml. (0.16 moles) of percent hydrogen peroxide at 0" C. A total of 22.8 ml. (0.160 moles) of trifluoroacetic anhydride was added to the above solution with stirring over a ten-minute period. Stirring was continued for another ten minutes. A mixture of 100 ml. of methylene chloride, 36 g. of sodium carbonate and 13.2 g. (0.0520 moles) of bisbutenylcarborane was placed in a threenecked round bottom flask. The flask was equipped with a mechanical stirrer, reflux condenser and a dropping funnel. The solution of trifiuoroperacetic acid was added dropwise over a 90-minute period. During this time, the temperature of the reaction was maintained below reflux by the use of an ice-water bath. After the addition Was complete, the mixture was refluxed for 30 minutes. Following the reflux period, reaction of a drop of the supernatant liquid to starch-iodide paper was negative, indicating the absence of peroxides. Gravity filtration of the reaction mixture followed by removal of solvent from the filtrate on a rotary evaporator gave 4.1 g. of a white solid. The sample was distilled under vacuum and the fraction which evolved at a head temperature of 200 C. was collected and crystallized. The colorless solid (10 g. representing a 67 percent conversion of alkenylcarborane to desired product) had a melting point range of 68-71 C. Gas chromatographic and infrared analyses indicated that the sample was better than percent pure and an elemental analysis was in excellent agreement with the calculated values.

Calcd. for B C H O B, 38.0; C, 42.3; H, 8.5 Found: B, 38.6; C, 42.5; H, 8.6

EXAMPLE 7 1,2-Bis(epoxypentyl)carborane: x=3

The procedure used for the preparation of bis(epoxybutyl) carborane was followed using the following amounts of reagents.

2.2 ml. 90 percent Hydrogen Peroxide (0.080 moles) 11.4 ml. Trifluoroacetic Anhydride (0.080 moles) 6.5 g. 1,2-Bis(4-pentenyl)carborane (0.021 moles) excellent agreement with the theoretical values.

Calcd. for B C H O B, 34.6; C, 46.2; H, 9.0 Found: B, 33.3; C, 45.3; H, 9.1

EXAMPLE 8 1,2-Bis(epoxyhexyl)carborane: x=4

The procedure used for the preparation of bis(epoxybutylcarborane was followed using the following amounts of reagents.

4.4 ml. of 90 percent Hydrogen Peroxide (0.16 moles) 22.8 ml. of Trifiuoroacetic Anhydride (0.160 moles) 13.6 g. of 1,2-Bis(5-hexenyl)carborane (0.043 moles) Calcd. for B C H O B, 31.8; C, 49.5; H, 9.4 Found: B, 31.3; C, 48.2; H, 9.4

EXAMPLE 9 1,2-Bis (epoxypropyl) carborane: x: 1

The procedure used for the preparation of bis(epoxybutylcarborane was followed except that disodium hydrogen phosphate was used as the bufler in place of sodium carbonate. The following amounts of reagents were used:

2.2 ml. of Hydrogen Peroxide (0.080 moles) 11.4 ml. of Trifluoroacetic Anhydride (0.080 moles) 3.5 g. of l,2-Bis(2-propenyl)carborane (0.016 moles) A total of 3.0 g. of product (representing an 83 percent conversion of alkenylcarborane to desired product) was isolated. Gas chromatographic and infrared analyses of the solid (melting point 36-48 C.) indicated a purity of 97 percent.

EXAMPLE 10 1,7-Bis(epoxybutyl)-neo-carborane: x=2

The procedure used for the preparation of bis(epoxybutyl)carborane was followed using the following amounts of reagents.

2.2 ml. of 90 percent Hydrogen Peroxide (0.080 moles) 11.4 ml. of Trifiuoroacetic Anhydride (0.080 moles) 6.6 g. of 1,7-Bis(butenyl)-neo-carborane (0.026 moles) The crude product was distilled under vacuum (0.1 mm.) and the fraction evolved at a head temperature of 150- 170 C. was collected and crystallized. The colorless solid (4.5 g. representing a conversion of 68 percent of alkenylneo-carborane to desired product) had a melting point range of 51-54 C. Gas chromatographic and infrared analyses of the product indicated a purity of 94 percent.

Adhesive Properties Excellent steel-on-steel adhesive strength is obtained when bis(epoxyalkyl)carboranes are cured with catalytic agents or reactive hardeners at temperatures above 100 C. under moderate pressure. Representative lap-shear strengths at room temperature are listed below for the epoxies cured with the catalyst, boron trifluoridezmonethylamine.

Lap-shear Example strength,

Epoxy number p.s.i.

Bis (epoxybutyDcarborane.-- 12 2, 320 Bis(epoxypentyl)carborane-- 13 2, 810 Bis(epoxyhexyl)earborane 14 3, 600

Representative lap-shear strengths at room temperature are listed below for the epoxies cured with the reactive hardener 4,4-diaminodiphenylsulfone.

Lap-shear strengths at 400 F. (air atmospheres-10 minute hold at temperature) as high as 980 p.s.i., have been obtained with the bis(epoxybutyl)carborane-3 phr. BF :EtNH catalyst systemExample 18.

Superior high temperature results are obtained by reacting the bis(epoxyalkyl)carboranes with certain reactive hardeners. Lap-shear strengths as high as 1730 p.s.i. have been obtained at 500 F. in air when bis(epoxybutyl)carborane wase cured with 4,4'-diaminodi.nhemllsulfone (Example Number 19). These values, which rep resent percent retention of room temperature strength (2040 p.s.i.) were obtained on samples which had been previously soake at 500 F. for two hours. Lap-shear strengths as high as 1460 p.s.i. at 500 F. in air have been obtained on samples soaked at 500 F. for 24 hours (Example Number 20). At 440 F., percent of roomtemperature lap-shear strength is retained (Example Number 21).

The following examples relate to preparation of lapshear test specimens, testing procedures, formulations for the various adhesive compositions and test results.

EXAMPLE 11 Preparation of Lap-Shear Specimens and Testing Procedures Percent Nitric Acid (70%) 10 Hydrofluoric Acid (50%) 2 Water 88 On removal from the acid solution, the adherends were thoroughly rinsed with cold water and then immersed in a chromic acid solution for ten minutes at F. The composition of the acid solution was as follows:

Sodium Dichromate g 28.5 Sulphuric Acid g 285 Tap Water To make 1 litre Aluminum Metal g 5 After the acid treatment, the adherends were thoroughly rinsed in cold running tap water. Finally, they were rinsed in distilled water, observed to make sure they held a continuous film of water, and dried in an oven for 30 minutes at 160 F. After the degreasing step, all handling was done using cotton gloves.

The adherends were laid up in a special mounting fixture which ensured accurate alignment of the adherends and an exact overlap of 0.50 in. The fixture could take a total of five specimens (ten adherends). The B- staged epoxy was warmed (212-300 F.-depending on the test sample) and carefully applied to the adherends. The latter were then warmed with an air gun and the liquid was spread over the overlap surfaces. In some cases, the fixture was placed in a vacuum oven at 212 F. for 15-20 minutes to outgas dissolved air in the epoxy, A 0.5 inch wide strip of glass cloth (Volan A-181 or 112) was laid over the overlap area of the lower adherend, and the upper adherend was then placed over the glass cloth. The lay-up fixture containing the specimens was placed in a Carver Hydraulic Press equipped,

with heating plates and a modified quick closer attachment to ensure constant pressure. After curing, the specimens were removed from the mounting fixture and filed to remove excess epoxy. The glue line thickness in each specimen was determined by measuring the thickness of each adherend adjacent to the overlap area with a micrometer, followed by measuring the total thickness at the overlap area. A simple subtraction gave the glue line thickness. All specimens were tested in an Instron Tensile Tester at a constant strain rate of 0.01 in./in./min. In elevated temperature tests, a specially designed furnace was preheated and placed around the specimen in the Instron Tensile Machine. A period of to minutes was required to bring the specimens to the test temperature. The specimen was held at that temperature for ten minutes and tested (at temperature).

EXAMPLE 12 Lap-Shear Strength: Bis(epoxybutyl)carborane- 3 phr. BF zEtNH Test Temperature F 75 Glue Line Thickness (in.) 0.003 Failure Strength, p.s.i 2320 Lap-Shear Strength Bis(epoxypentyDcarborane-S phr. BF :EtNI-I Test Temperature F. 75 Glue Line Thickness (in.) 0.006 Failure Strength, p.s.i 2810 Composition-1.0 g. epoxy+0.030 g. catalyst B-stage225260 F. for minutes Outgassed-No Glass ClothStyle 181 Cure-Assembly445 F., 120 p.s.i., 1 hour Post-CureNone EXAMPLE 14 Lap-Shear Strength Bis(epoxyhexyl)carborane-3 phr. BF zEtNH Test Temperature, F 75 Glue Line Thickness (in.) 0.007 Failure Strength, p.s.i 3600 Composition-1.02 g. epoxy+0.03 g. catalyst B-stage-230265 F. for 30 minutes Outgassed-No Glass Cloth-Style 181 Cure-Assemb1y-445, 120 p.s.i., 1 hour Post-Cnre-None EXAMPLE 15 Lap-Shear Strength Bis(epoxypropyl)carborane-48 phr. 4,4'-diaminodiphenylsulfone Test Temperature, F 75 Glue Line Thickness (in.) 0.003 Failure Strength, p.s.i 1740 Composition-4.52 g. epoxy+0.73 g. hardener B-stage--300 F. for mniutes 'Outgassed-Yes Glass ClothStyle 112 Cure-Assembly-390 F., 120 p.s.i., 2 /2 hours -8 EXAMPLE 16 Lap-Shear Strength Bis(epoxybutyl)carborane-47 phr. 4,4'-diaminodiphenylsulfone Test Temperature, F. 75 Glue Line Thickness (in.) 0.005 Failure Strength, p.s.i 2040 Composition1.51 g. epoxy-F071 g. hardener B-stage300 F. for 40 minutes OutgassedYes Glass ClothStyle 112 Cure-Assembly390 F p.s.i., 2 /2 hours Post-Cure--None EXAMPLE 17 Lap-Shear Strength Bis(epoxybutyl)-neo-carborane-28 phr. 4,4'-diaminodiphenlysulfone Test Temperature, F. 75 Glue Line Thickness (in.) 0.004 Failure Strength, p.s.i 2000 EXAMPLE 18 Lap-Shear Strength Bis(epoxybutyl)carborane-3 ph. BF :EtNH

Test Temperature, F. 400 Glue Line Thickness (in.) 0.007 Failure Strength, p.s.i 980 CompositionZOl g. epoxy+0.06 g. catalyst B-stage--212 F. for 1 hour OutgassedYes Glass Cloth-None Cure-Assembly445 F., 120 p.s.i., 1 hour Post-Cure-None EXAMPLE 19 Lap-Shear Strength Bis(epoxybutyl)carborane-47 phr. 4,4'-di-aminodiphenylsulfone Test Temperature, F 500 Glue Line Thickness (in.) 0.006 Failure Strength, p.s.i 1730 Composition1.51 g. epoxy+0.71 g. hardener B-stage-300 F. for 40 minute Outgassed--Yes Glass Cloth-Style 112 Cure-Assembly390 'F., 120 p.s.i., 2 /2 hours Post-Cure-500 F. for 2 hours EXAMPLE 20 Lap-Shear Strength Bis(epoxybutyl)carborane-48 phr. 4,4'-diami0ndipheny1- sulfone Test Temperature, F 500 Glue Line Thickness (in.) 0.004 [Failure Strength, p.s.i 1460 Composition1.51 g. epoxy+0.73 g. hardener B-stage-300 F. for 45 minutes OutgassedYes Glass ClothStyle 112 Cure-Assembly390 F., 120 p.s.i., 2 hours Post-Cure--24 hours at 500 F.

9 EXAMPLE 21 Lapwshear Strength Bis(epoxybutyl)carborane-30 phr. 4,4'-diaminodiphenylsulfone Test Temperature, F. 400 Glue Line Thickness (in.) 0.004 Failure Strength, p.s.i 1880 We claim:

1. An adhesive composition possessing adhesive properties at temperature and high temperature comprising 1,2- Bis(epoxyalky1)carboranes of the following structure 0137011 (CH3) C\'6-/"C (CH2) 1 (IE-70H:

mHio 0 where x=1, 2, 3, or 4 or the isomeric structure 1,7-Bis (epoxybutyl)-neo-carborane with a curing agent selected from the group consisting of:

boron tri fluoride-monoethylamine;

tri (dimethylaminomethyl) phenol; and

N N-dimethylbenzylamine.

2. An adhesive composition possessing adhesive properties at room temperature and high temperature comprising 1,2-Bis(epoxyalkyl)carboranes of the following structure where x=1, 2, 3, or 4 or the isomeric structure 1,7-Bis (epoxybutyl)-neo-carborane with the reactive hardener 4 4'-diaminodiphenylsulfone.

References Cited UNITED STATES PATENTS 7/1966 Shepard 260-2 3/1969 Drinkard et a1. 260-462 OTHER REFERENCES Barnes et al., High-Temperature Epoxycarborane Adhesives, Chem. Abst. 71, 71544g (1969).

Spiker et a1., Adhesives in Space-AppolIo and Future Manned Spacecraft, Chem. Abstracts 74, 65112K (1971).

Lee et al., Handbook of Epoxy Resins, pp. 6-3, Mc- Graw-Hill, 1967, TP 1180E6 L4.

Inorganic Chemistry 2, 1097-1105 (1963).

WILLIAM H. SHORT, Primary Examiner E. A. NIELSEN, Assistant Examiner US. Cl. X.R. 156-430 

